Conductive pattern refers to a conductive pattern that contains both an organic component including a resin and an inorganic component including a conductive filler or the like.
A so-called polymer-type conductive paste with a large amount of a particulate silver flake or copper powder, or carbon particles mixed in a resin or an adhesive for forming an organic-inorganic composite conductive pattern as described above has come into practical use.
Many of polymer-type conductive pastes put into practical use form a pattern by a screen printing method and heating and curing the pattern to form a conductive pattern (Japanese Patent Laid-open Publication No. 02-206675 and Japanese Patent Laid-open Publication No. 2007-207567).
To accurately draw a pattern of 100 μm or less, a conductive paste capable of being acid-etched (Japanese Patent Laid-open Publication No. 10-64333) and a photosensitive curable conductive paste (Japanese Patent Laid-open Publication No. 2004-361352 and WO 2004/61006) are disclosed.
However, it is difficult to accurately draw a pattern of 100 μm or less by the screen printing methods disclosed Japanese Patent Laid-open Publication No. 02-206675 and Japanese Patent Laid-open Publication No. 2007-207567.
The conductive paste described in Japanese Patent Laid-open Publication No. 10-64333 has the problem that, to perform patterning by a photolithography method, it is necessary to form a resist layer on a coating film, leading to an increase in the number of steps. In the methods described in Japanese Patent Laid-open Publication No. 2004-361352 and WO 2004/61006, a fine pattern is easily obtained by imparting photosensitivity. However, the method in Japanese Patent Laid-open Publication No. 2004-361352 leads to low conductivity, and the method described in WO 2004/61006 requires that the acryl (methacryl) equivalent be reduced to exhibit conductivity so that a conductive pattern obtained using this method is fragile. Hence, it is difficult to apply onto a flexible substrate and poor in adhesion to an ITO (indium tin oxide) electrode on a glass or film base material.
It could therefore be helpful to provide a photosensitive conductive paste capable of forming a conductive pattern having high adhesion to ITO on a base material, can be finely patterned, can exhibit conductivity at a relatively low temperature, and has flexibility if necessary; and a method of producing a conductive pattern.